Mineralogy of Siliceous Hot Springs Deposits:Mineralogy of Siliceous Hot Springs Deposits:

Comparing Earth and MarsComparing Earth and Mars

InternVicki Mills

MentorProf. Jack Farmer

(Ruff, 2008)

Opaline Silica Deposits

(>90% Silica)

Mini-TES SpectraMini-TES Spectra

(Ruff, S., J. Farmer, W. Calvin et al. 2007. Evidence for possible siliceous sinter at Home Plate in Gusev Crater Eos Transactions, American Geophysical Union, Fall Meeting Suppl, Abstract, P23A-1097)

Transformational Sequence Transformational Sequence for Silica (SiOfor Silica (SiO22) Polymorphs) Polymorphs

Opal-A (SiO2.n

H2O)Opal-C/T Quartz

Amorphous Paracrystalline Microcrystalline

Preservation Potential

Low High

Decrease in porosity, permeability & structural H20

2-theta peaks: 20-24° 2-theta peaks: 20.8°2-theta curve: centered at 22°

Opaline Silica (Opal-A) forms in Opaline Silica (Opal-A) forms in Hot Spring EnvironmentsHot Spring Environments

Study LocationsStudy Locations::

Excelsior Geyser, Excelsior Geyser, Yellowstone National Yellowstone National Park, WyomingPark, Wyoming

Orakei Korako, Orakei Korako,

New ZealandNew Zealand

Steamboat Steamboat Springs, NevadaSprings, Nevada

X-Ray Powdered Diffraction (XRPD)X-Ray Powdered Diffraction (XRPD)

Sample Sample PreparationPreparation Mortar & PestleMortar & Pestle Sieved 150Sieved 150μμmm

Run ConditionsRun Conditions Siemens D-5000Siemens D-5000 40kV at 30mA40kV at 30mA CuKCuKαα Radiation Radiation Step size 0.03-0.05°Step size 0.03-0.05°

For JADE Analysis

Sample PreparationSample Preparation 3g sample + 0.33g 3g sample + 0.33g

ZnOZnO Crushed <20Crushed <20μμm m

w/micronising millw/micronising mill

Run ConditionsRun Conditions Siemens D-5000Siemens D-5000 40kV at 30mA40kV at 30mA CuKCuKαα Radiation Radiation Step Size 0.0163Step Size 0.0163

For Rock Jock Analysis

Sample Preparation

New Zealand

JADE XRPD Results

Yellowstone

Steamboat

New Zealand

Qua

rtz

Opa

l-C/T

Amorphous Curve Centered at 22° 2θ

Opa

l-AO

pal-A

Clay Profile

Rock Jock ResultsRock Jock Results

0.00%10.00%20.00%30.00%40.00%50.00%60.00%70.00%

Opal-A Illite Smectite

OpalineSilica

Clays

Steamboat

Yellowstone

63.8 61.7

20.0 22.112.3 11.9

Thin Section AnalysisThin Section Analysis

Finely laminated sinter

Coniform Fabric

Characterization of Thin SectionsCharacterization of Thin Sections

Microbial fossil assemblage

(20X)(10X)

Calothrix (thermophilic cyanobacterium; filaments are ~30μm in diameter)

Phormidium (thermophilic cyanobacterium; filaments are ~5μm in diameter)

35-59°C

<35°C

InterpretationsInterpretations Similarities between mini-TES spectra of high silica Similarities between mini-TES spectra of high silica

deposits at Home Plate and those of opaline siliceous deposits at Home Plate and those of opaline siliceous sinter from hot springs on Earth, suggests a common sinter from hot springs on Earth, suggests a common origin. On earth, siliceous sinters have been shown to origin. On earth, siliceous sinters have been shown to preserve a diverse fossil record of microbial life. preserve a diverse fossil record of microbial life.

This interpretation is consistent with the geological This interpretation is consistent with the geological setting of Home Plate, which has been interpreted to be setting of Home Plate, which has been interpreted to be an explosive volcanic feature. Two alternative an explosive volcanic feature. Two alternative hypotheses have been suggested: Thermal spring hypotheses have been suggested: Thermal spring deposits, or fumerolic deposits. It is not possible to deposits, or fumerolic deposits. It is not possible to choose based on current evidence!choose based on current evidence!

Other outstanding issues: On Earth, opaline sinters Other outstanding issues: On Earth, opaline sinters quickly transform to ordered phases, like quartz. quickly transform to ordered phases, like quartz. However, it appears that even after billions of years on However, it appears that even after billions of years on Mars, the high silica deposits at Home Plate have not Mars, the high silica deposits at Home Plate have not undergone any significant digenetic transformation. undergone any significant digenetic transformation. Why?Why?